BALI, Indonesia (CNN) -- The United Nations climate change conference headed toward its conclusion Friday, with the United States and the European Union trying to resolve an impasse over how developed nations should tackle global warming.

Al Gore: "My own country, the United States, is principally responsible for obstructing progress here in Bali."

Japan and Canada have taken positions in line with the United States, while Australia's position is uncertain.

Negotiations over an agreement to replace the 10-year-old Kyoto Protocol, which expires in 2012, continued all night, officials told CNN, but disagreements remained.

The Europeans are pushing for an agreement that contains specific numbers for emissions cuts, but Washington wants to leave maneuvering room for future negotiations, including next month's U.S.-sponsored climate talks in Hawaii.

The EU delegation has balked at that stance, saying it would render January's major emitters meeting "meaningless."

"We are disappointed that having reached this stage of the negotiations we still haven't heard from the United States," said said Humberto Rosa, a member of the European delegation and Portuguese secretary of state for the environment.

"What is their exact level of ambition or of engagement in the Bali roadmap?"

Former U.S. Vice President Al Gore, fresh from accepting the Nobel peace prize for his work on climate change awareness, sided with the Europeans.

In an interview with CNN, U.N. Secretary-General Ban Ki-moon leaned toward the United States' position, stressing that Bali negotiations have to be "based on realistic and practical assessment."

"Somewhere down the road, quantifiable targets on emissions reductions" would be discussed, he said, adding that "launching the process [is] very important."

Washington is balking at suggestions by the EU that any agreement to replace the Kyoto Protocol on global warming should require developed countries to cut their emissions by 25 to 40 percent of 1990 levels by 2020.

The Bush administration says Europe is moving too fast.

"The main effort here in Bali is to get all of the countries to agree, in concept, that they will collectively support a long-term global goal for reducing emissions," said James Connaughton, the chairman of the White House Council on Environmental Quality. "That's the first step before you can then sit down and work through the specifics of what that goal might be."

The shrill tone of Thursday's public statements indicated the behind-the-doors negotiations were difficult.

Rosa said the European delegation said it is not "blackmailing" Washington, but said it is "logic[al]" that if no deal is completed in Bali, it cannot be built upon in Hawaii.

The Kyoto Protocol was passed 10 years ago by the United Nations Framework Convention on Climate Change with the goal of limiting greenhouse gas concentrations in the atmosphere.

While 175 nations and the European Economic Community have ratified it, the United States has not.E-mail to a friend